Disclosed are intermediate transfer members, and more specifically, intermediate transfer members useful in transferring a developed image in an electrostatographic, for example xerographic, including digital, image on image, and the like, machines or apparatuses and printers. In embodiments, there are selected intermediate transfer members comprised of surface treated carbon black, or more specifically, wherein a carbon black and a polypyrrole (PPy) are subjected to an in situ polymerization forming a polypyrrole grafted carbon black that is subsequently dispersed or mixed with a polymeric solution, such as a polyamic acid solution, to thereby provide intermediate transfer components like belts with a tunable preselected resistivity, where the polymeric solution is, for example, polyamic acid solution as illustrated in copending applications U.S. application Ser. No. 12/129,995, U.S. application Ser. No. 12/181,354, and U.S. application Ser. No. 12/181,409, the disclosures of which are totally incorporated herein by reference.
A number of advantages are associated with the intermediate transfer member, such as a belt (ITB) of the present disclosure, such as a tunable resistivity by, for example, the loading or amount of the PPy-grafted carbon black, the PPy grafting amount with a fixed loading, or both, where the surface resistivity is readily tuned to, for example, from about 108 to 1013 ohm/sq; excellent dimensional stability; acceptable conductivities; a variety of formulation latitudes for the disclosed ITB as compared to an ITB with an untreated carbon black; ITB humidity insensitivity for extended time periods; excellent dispersability in a polymeric solution; low and acceptable surface friction characteristics; and simplified economic methods for ITB formation.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member, and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles and colorant. Generally, the electrostatic latent image is developed by contacting it with a developer mixture comprised of a dry developer mixture, which usually comprises carrier granules having toner particles adhering triboelectrically thereto, or a liquid developer material, which may include a liquid carrier having toner particles dispersed therein. The developer material is advanced into contact with the electrostatic latent image, and the toner particles are deposited thereon in image configuration. Subsequently, the developed image is transferred to a copy sheet. It is advantageous to transfer the developed image to a coated intermediate transfer web, belt or component, and subsequently transfer with a high transfer efficiency the developed image from the intermediate transfer member to a permanent substrate. The toner image is subsequently usually fixed or fused upon a support, which may be the photosensitive member itself, or other support sheet such as plain paper.
In electrostatographic printing machines wherein the toner image is electrostatically transferred by a potential difference between the imaging member and the intermediate transfer member, the transfer of the toner particles to the intermediate transfer member and the retention thereof should be substantially complete so that the image ultimately transferred to the image receiving substrate will have a high resolution. Substantially about 100 percent toner transfer occurs when most or all of the toner particles comprising the image are transferred, and little residual toner remains on the surface from which the image was transferred.
Intermediate transfer members possess a number of advantages, such as enabling high throughput at modest process speeds; improving registration of the final color toner image in color systems using synchronous development of one or more component colors and using one or more transfer stations; and increasing the number of substrates that can be selected. However, a disadvantage of using an intermediate transfer member is that a plurality of transfer operations is usually needed allowing for the possibility of charge exchange occurring between toner particles and the transfer member which ultimately can lead to less than complete toner transfer resulting in low resolution images on the image receiving substrate, and image deterioration. When the image is in color, the image can additionally suffer from color shifting and color deterioration.
It is desired that the intermediate transfer member have a controlled resistivity, wherein the resistivity is substantially unaffected by changes in humidity, temperature, bias field, and operating time. In addition, a controlled resistivity is of value so that a bias field can be established for electrostatic transfer. Also, it is of value that the intermediate transfer member not be too conductive as air breakdown may occur, and that the resistivity thereof be reproducibly tuned, that is for example, where the resistivity of the transfer member can be selected prior to its incorporation into a xerographic apparatus.
Attempts at controlling the resistivity of intermediate transfer members by, for example, adding conductive fillers, such as ionic additives and/or carbon black to the outer layer, are disclosed in U.S. Pat. No. 6,397,034 which describes the use of fluorinated carbon filler in a polyimide intermediate transfer member layer. However, there can be problems associated with the use of such fillers in that undissolved particles frequently bloom or migrate to the surface of the fluorinated polymer and cause imperfections to the polymer, thereby causing nonuniform resistivity, which in turn causes poor or unacceptable antistatic properties and poor or unacceptable mechanical strength characteristics. Also, ionic additives on the ITB surface may interfere with toner release. Furthermore, bubbles may appear in the polymer, some of which can only be seen with the aid of a microscope, and others of which are large enough to be observed with the naked eye resulting in poor or nonuniform electrical properties and poor mechanical properties.
In addition, the ionic additives themselves are sensitive to changes in temperature, humidity, and operating time. These sensitivities often limit the resistivity range. For example, when ionic additives are present, the resistivity usually decreases by up to two orders of magnitude or more as the humidity increases from about 20 percent to 80 percent relative humidity. This effect limits the operational or process latitude.
Moreover, ion transfer can also occur in these systems. The transfer of ions leads to charge exchanges and insufficient transfers, which in turn causes low image resolution and image deterioration, thereby adversely affecting the copy quality. In color systems, additional adverse results include color shifting and color deterioration. Ion transfer also increases the resistivity of the polymer member after repetitive use. This can limit the process and operational latitude, and eventually the ion filled polymer member will be unusable.
A number of the known ITB formulations apply carbon black (CB) or polyaniline as the conductive species; however, this has some limitations. For example, polyaniline is readily oxidized and results in loss of conductivity, its thermal stability is usually limited to about 200° C., and it begins to lose its conductivity at above 200° C. Also, it can be difficult to prepare carbon black based ITBs with consistent resistivity since the required loadings reside on the vertical part of the percolation curve.
Therefore, it is desired to provide a controlled resistivity tunable intermediate transfer member, which has excellent transfer capabilities, possesses excellent humidity insensitivity characteristics leading to high copy quality where developed images with minimal resolution issues can be obtained. It is also desired to provide a weldable intermediate transfer belt that may not, but could, have puzzle cut seams, and instead has a weldable seam, thereby providing a belt that can be manufactured without labor intensive steps, such as manually piecing together the puzzle cut seam with fingers, and without the lengthy high temperature and high humidity conditioning steps. In addition, with the selection of the disclosed polypyrrole-grafted carbon black as the conductive filler, the resistivity of the intermediate transfer member like a belt (ITB) can be reproducibly tuned to desired levels where, for example, as the amount of the PPy grafted onto the carbon black surface is increased, the higher the surface resistivity.